Understanding Gauge Meters

#1
(extract from old forum)

Critical meters are:

1. Oil Temp

Engine oil is the lifeblood of the whole engine block. It lubricates and protects mechanical parts from excessive wear. However the engine oil has its heat limitation before it reached its flashpoint and starts to breakdown. For such sensor, it is best to attach it to the oil pan or a sandwich between the oil filters. It is important to know that if oil temperature is hitting 130 to 140C, your oil is about being cooked. This means that a judgment call is needed for a bigger radiator, and/or a bigger fan, and/or oil cooler.

2. Water Temp

Water or coolant acts to cool the engine and oil by means of a heat exchange via the radiator. This is one very important parameter to monitor as the OEM gauge is rather inaccurate as there is no numeric indication. It is interesting to know that water temp is more or less equal or higher (usually the case) then the oil temp, and if it is shooting pass 110C to 130C, then it could mean that your fan is not coping, a lower thermostat is needed, the OEM radiator is not coping or that there is a leak somewhere.

3. Exhaust Temp

The exhaust temperature is a little more tricky here but basically it monitor how your pistons are coping depending on the engine, it should stabilize at one point but if it continues to go up then it could mean that the current AF ratio and ignition timing is not right, or that the current cooling system is not efficient for heat control.

4. Boost (or intake manifold Pressure)

Boost and intake manifold pressure basically shows you how much pressure the FI system is pumping into your combustion chamber. The regular boost meter shows the positive pressure, and the intake manifold shows you a range from negative to positive. However for intake manifold pressure, the positive pressure shown is pretty limited.

Good to have meters are:

1. Oil Pressure

This meter basically shows you how much oil pressure you have and it’s important should you have large oil coolers. You need to know what sort of pressure you have while you engine is at optimum point and should you loss pressure that is an indication that there is a leak some where, and if you should be driving, you need to back off from the accelerator.

2. Fuel Pressure

For Defi, this is a pretty good gauge to have, as it will work together with the boost gauge to give you a pressure differential. This is very important for FI cars as if you are not having enough fuel pressure in accordance to the amount of boost, then one is just playing for time before detonation occurs.

With all these meters, there is no hard and fast rules to it but it helps you understand the condition of the engine while it is running and helps you make a better judgment call when needed....
 
#2
A little more to add re. engine oil temp.

Typical flash point of PAO-based Synthetics: ~ 450 oF / 230 oC. So at 130 oC, you can expect higher degree of degradation of the baseoil and additives. Will not be a case of total oil breakdown tho, but rather the accelerated wear rate of the other equipment at that temperature.

And definition of flash point is the temperature at which vapor starts to appear at a given pressure.

Cheers and have fun.
 
#3
oil pressure

Isit normal for stock to have a lower oil pressure?just fixed a defi oil temp car is onli few days old.at idling oil pressure ais at 0.8-1.1. when half clutch it will drop to 0.5-0.6.when moving it is at 4.0-5.0. Car still running in.mechanic told me tat it is because stock engine oil from japan too thin tast why,isit true?and if oil pressure fall belows 1 isit normal?before this car was driving WRX at idling the oil pressure is at 0.4-0.6.Is evo running at lower oil pressure?
Thanks for ur valuable info in advance.
 

Privateer

Well-Known Member
#4
Assuming stock oil thermostat, and depending on where the oil pressure sensor is located, 1 to 1.2 bar of oil pressure is typical. If it falls below 1 bar it might be worth your time to have it checked.
 

ejay20tee

Well-Known Member
#5
Re: oil pressure

89er said:
Isit normal for stock to have a lower oil pressure?just fixed a defi oil temp car is onli few days old.at idling oil pressure ais at 0.8-1.1. when half clutch it will drop to 0.5-0.6.when moving it is at 4.0-5.0. Car still running in.mechanic told me tat it is because stock engine oil from japan too thin tast why,isit true?and if oil pressure fall belows 1 isit normal?before this car was driving WRX at idling the oil pressure is at 0.4-0.6.Is evo running at lower oil pressure?
Thanks for ur valuable info in advance.
Ej20T block is a flat four, the oil pump doesnt have to work so hard to pump oil thru the block. My Sti used to be at about 1bar during idle too.

Evo typically is about .4-.6 . I am using 40W oil for mine.
When revs build the pressure goes up...so its nothing to worry about.
If u r still worried about lo pressure during idle, u can always change ur oil pump.

:D
 
#6
Mine is about 0.9 to 1.1 during idle after warm-up but it goes up to 6 when high rev. And sometime it drops to about 0.5 when stopping.

I am not sure if this a problem, i am currently using Motul Chrono Competition 15/50.
 

burnings

Well-Known Member
#7
IMHO, the only useful gauge is the Boost, the rest are sorta cosmetics. If ur water or oil temp goes beyond, itz already damaged done. So watz the point?
 

DoggieHowser

Moderator
Staff member
#8
burnings said:
IMHO, the only useful gauge is the Boost, the rest are sorta cosmetics. If ur water or oil temp goes beyond, itz already damaged done. So watz the point?
I guess then the boost gauge is also optional.

:)

For most of us who drive the Evo hard, on track, keeping track of the gauges (including the fuel gauge ;)) is the best way to make sure you aren't flogging your engine.

Maybe maybe you really like rebuilding your engines.
 

ghoonk

Active Member
#9
Re:

Privateer said:
Assuming stock oil thermostat, and depending on where the oil pressure sensor is located, 1 to 1.2 bar of oil pressure is typical. If it falls below 1 bar it might be worth your time to have it checked.
I'm running a Tomei oil thermostat. Oil Pressure when idling is around 2 bar, and at WOT goes as high as 9 bars.
 
#10
Hi all

Just install defi exhaust temp gauge

My sensor hole drilled at one part of the manifold before 4 combines into 1. .

Warning set at 800c.

Keeps rising when accelerating but drops once off throttle.

Will hit 950cc at prolonged throttle.

Any advise.

Regards
 

JudgeJules

Moderator
Staff member
#11
GAULTAN said:
Hi all

Just install defi exhaust temp gauge

My sensor hole drilled at one part of the manifold before 4 combines into 1. .

Warning set at 800c.

Keeps rising when accelerating but drops once off throttle.

Will hit 950cc at prolonged throttle.

Any advise.

Regards
I would think that your AFR is a bit out, hence when on boost the engine is running lean and probably knocking quite abit thus raising Exos temp.
 

Privateer

Well-Known Member
#12
JudgeJules said:
I would think that your AFR is a bit out, hence when on boost the engine is running lean and probably knocking quite abit thus raising Exos temp.
If there really is knock, EGT goes down. The reason is that the boundary layer has broken down, and heat from the combustion has been released into the piston crown, cylinder wall and rods instead of being a controlled burn and exiting through the valves in the form of exhaust gases.

950 degC is typical for the probe location (before turbo).
 
#13
Privateer said:
JudgeJules said:
I would think that your AFR is a bit out, hence when on boost the engine is running lean and probably knocking quite abit thus raising Exos temp.
If there really is knock, EGT goes down. The reason is that the boundary layer has broken down, and heat from the combustion has been released into the piston crown, cylinder wall and rods instead of being a controlled burn and exiting through the valves in the form of exhaust gases.

950 degC is typical for the probe location (before turbo).
Hi

Thanks for the help guys.

Hi Privateer,

Yup its way before the turbo and at one part of the 4 before it merges into 1.

I would be safe yeah ?

Best Regards
 

burnings

Well-Known Member
#15
nutboy said:
is ther a diff btw gauges?example delfi and prosports?better brand give better & accurate readings?need some advice as wan to install :lol:
Defi gives much accurate reading than prosport!!!! Itz Taiwan vs Japan quality leh....
 
#17
Would A/F or knock meter be more useful since it measures the engine activity straight off?
Not only does it help in tuning, it also brings to light engine problems much sooner before the other "symptoms" start to show (eg. increasing temp, etc)

The HKS A/F Knock Amp looks tempting but a tad expensive.
 

burnings

Well-Known Member
#18
acepraeshugyosha said:
Would A/F or knock meter be more useful since it measures the engine activity straight off?
Not only does it help in tuning, it also brings to light engine problems much sooner before the other "symptoms" start to show (eg. increasing temp, etc)

The HKS A/F Knock Amp looks tempting but a tad expensive.
Get the A/F will do. Knocking is common even in stock cars. :)
 

kik

Well-Known Member
#20
I'll try to find a pic guys. Its of a guy driving at 70kmh, with his pro gauge meters, doing 2 bar of boost...LOL
 

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